When an antibiotic has been administered during an extended period of time, pathogenic bacteria to be targeted has been removed, but fungi resistant to antibiotics have increased. It is considered that such a situation causes deep-seated mycoses (The phenomenon in which remaining fungi remarkably increase is designated as so-called microbial substitution). Alternatively, an elderly patient, a postoperative patient, or a patient to whom an antitumor drug or an immunosuppressant is administered is subject to fungal infection, due to the suppressed biophylaxis. It is considered that fungi increased in such a patient cause deep-seated mycoses.
Therapeutic agents for deep-seated mycoses include antifungal drugs, for example, 1) a nucleic acid base drug flucytosine, based on the inhibition of DNA synthesis in fungi, and 2) a polyene macrolide amphotericin B, an imidazole derivative miconazole, and a triazole derivative fluconazole, based on the inhibition of synthesis of cell membrane in fungi.
Ferrichrome, a cyclic hexapeptide containing three ornithines, having the following chemical structure is a known compound (non-patent literature 1), but this reference does not disclose that ferrichrome has an antifungal activity.
    [non-patent literature 1] Journal of American Chemical Society, 1980, vol. 102, pp. 4224-4231